The present invention is directed to a novel and improved means for engaging and removing a ply of limp material, typically a piece of fabric, from a stack of such plies. In the production of garments, for example, it is conventional practice to cut simultaneously an entire stack of garment sections from a stacked lay-up of fabric sections. The cut stack of fabric sections is then transferred to a subsequent production operation, in which the sections are removed one at a time for sewing, etc.
In a continuing effort to automate production operations of all kinds, substantial effort has been devoted to the development of systems capable of lifting off and separating the uppermost ply of fabric from a stack of pre-cut fabric sections and transporting the separated ply to a desired location for performance of a production operation. Prior proposals for this purpose have involved the use of means such as suction devices or pressure sensitive tapes, for example, for lifting off the top ply of a stack. Other arrangements heretofore proposed have involved the use of needle-like elements for engaging and lifting off the uppermost ply of a stack. A still further proposal for this purpose is represented by the Lutts et. al. U.S. Pat. No. 3,756,587.
Many of the above mentioned prior proposed arrangements are effective at a certain level, but each has disadvantages of one kind or another which limits its usefulness. For example, in an operation in which all conditions are fixed, with a single size and shape of ply and with the ply being at all times of the same material, it is frequently possible to adjust and adapt one or more of the various prior art devices for operation at a reasonable level of efficiency. However, in a more typical operation, the equipment may be called upon to handle parts of a variety of sizes and/or shapes and also to handle parts of different materials for which the prior art devices are not well suited. Even where a production operation involves only a single size and shape of part, serious problems may be experienced in dealing with a plurality of materials on different occasions. All of the prior art systems, insofar as the applicant is aware, have significant shortcomings in an environment requiring the handling of a variety of materials and/or shapes.
It is an object of the present invention to provide, in an apparatus for nipping and lifting a limp ply from a stack, a lifting unit for lowering and lifting a ply picking unit, whereby the pressure applied by the ply picking unit to the top ply of the ply stack may be accurately controlled. In its broadest aspect, the present invention consists of an apparatus for nipping and lifting a limp ply, supported by a lifting unit for controllably lowering and lifting the ply picking unit. The ply picking unit is supported at one end of a lifting lever, which is pivotally mounted on a supporting frame structure. An actuator, operable through a predetermined stroke, is also pivotally mounted on the frame stucture and interconnected with the lifting lever by a slideable connecting means. The lifting lever is substantially balanced by a balancing means which acts independently of the actuator. Moreover, an adjustable, yieldable means is associated with the actuator means and slideable connecting means, whereby the force imparted by the actuator means to the lifting lever may be accurately controlled.
The unique combination of a substantially balanced lifting lever, operated by an adjustable actuating force permits a lever action for lowering and lifting a ply picking unit that is positive in operation and accurately adjustable to control the pressure contact between the ply picking unit and the top ply. It is to be understood that different ply materials may have widely different characteristics of stiffness, thickness, weight, roughness or smoothness, susceptibility to damage or marking, etc. The apparatus of the invention uniquely accommodates such variable conditions by permitting the adjustment and accurate control of the pressue applied by the ply picking unit to the ply of a ply stack. While not critical to the present invention, the apparatus described herein is ideally suited for use in combination with the picking apparatus for nipping and lifting a limp ply which is described and claimed in copending application of Kenneth O. Mortion, Ser. No. 471,029, filed May 17, 1974, now U.S. Pat. No. 3,940,125, which is hereby incorporated by reference.
For a better understanding and appreciation of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment and to the accompanying drawings. It should especially be understood that many of the features of the invention may be used to advantage individually as well as in association with some or all of the other features.